Hitherto, paste-like adhesives and adhesive materials obtained by coating an adhesive on heat-resistant substrates are known as adhesives for the fixing treatment of electric and electronic parts, such as semiconductor chips, substrates, lead frames, etc. The adhesives used are thermosetting resin adhesives such as epoxy resin adhesives, acrylic resin adhesives, or rubber-phenol adhesives. However, these adhesives have various problems that because high temperature and long time are required for heat curing, the adhesion workability is poor; a large amount of volatile components are generated in heat curing the adhesive and the volatile components thus generated soil leading wires; and because the adhesives have a high hygroscopic property, an encapsulating resin package of a semiconductor chip is cracked in reflowing a solder. Thus, it is hard to say that the conventional adhesives have a high reliability necessary for the adhesives for the fixing treatment of electric and electronic parts, and sufficiently satisfactory adhesives have not yet been obtained.
Also, a hot melt-type film adhesive using a polyimide resin can be heat-press adhered to an adherend in a short period of time, and where using the adhesive, a heat-curing step after adhering is unnecessary. However, the adhesive has a high glass transition point and a very high temperature is required for working. Therefore, there is a large possibility of giving heat damages to the adherend.
On the other hand, when an adhesive having a low glass transition point is used for giving a low-temperature workability, the heat resistance is poor and the reliability is decreased.
Furthermore, it is known that polycarbodiimide which has hitherto been widely used has a high heat resistance, and workability thereof is relatively good as compared with the polyimide resin adhesive. However, although the polycarbodiimide shows a low hygroscopic property under room temperature atmosphere, when the polycarbodiimide is allowed to stand under a humidified condition at high temperature and high pressure, such as a pressure cooker test (PCT), the polycarbodiimide is easily hydrolyzed to decrease the molecular weight and also the mechanical strength, thereby the polycarbodiimide cannot endure the practical use for electronic materials used for semiconductor elements, etc.